The present invention relates to a furcation apparatus for conductors of a multi-conductor ribbon or cable. More specifically, the present invention describes a furcation apparatus for use with ruggedized fanout or furcation assemblies which use strength members such as aramid fiber reinforcements for longitudinal strength.
The present invention is described herein in relation to optical fibers of multi-fiber ribbons or cables. However, it is contemplated that the invention is equally applicable and useful for conductor types other than optical fibers. For example, the furcation apparatus described herein may be used with electrical conductors such as micro-coaxial conductors which are part of a multi-conductor cable. Therefore, references herein to optical fibers and optical fiber cables are also intended to include electrical conductors and their associated cables.
The use of fiber optic cables in applications such as telecommunication networks, cable TV networks, and data communication networks is well known. The advantages of using fiber optic systems include a broader bandwidth for signal transmission and inherent immunity to electro magnetic interference. Because of these advantages, the use of fiber optic cables is becoming more and more common. Therefore, it becomes increasingly important to have components for use with fiber optic cables which are easy to use and manufacture.
The appearance of fiber optic cables generally resembles that of electrical cables. Fiber optic cables typically comprise optical fibers and other cable elements which are protected from the external environment by an external jacket. Typically, a strength member such as an aramid fiber is placed within the outer jacket for additional longitudinal strength in the cable. Alternately, the cables may be of a loosely bundled type with the optical fibers contained loosely within the tubes or ducts in a cable core. Again, a strength element such as an aramid fiber may also be included.
To make connections to individual optical fibers, the individual optical fibers must be separated from each other for connectorization. Typically, each of the individually exposed fibers is protected by what is known in the art as a furcation tube or fanout tube. Typical furcation tubes consist of an inner tube for receiving the optical fiber. The inner tube is surrounded by a strength member such as an aramid fiber and an outer jacket to provide environmental protection. It is both necessary and desirable to protect each of the optical fibers when transitioning from the multi-fiber cable to the individual furcation tubing. Thus, to make the installation of fiber cables reliable and efficient a furcation unit is needed which allows individual optical fibers to be easily handled, connectorized and spliced. The furcation unit must protect the fibers in the transition region between the multi-fiber cable and the furcation tubes.
Furcation kits sometimes do not adequately protect or secure different members of the furcation, or are very difficult to assemble. In addition, some furcation kits require the use of tools or encapsulants which complicate their use. Methods and devices for furcation which do not require specialized tools or encapsulants offer distinct advantages when assembling the fiber optic cables. In addition, having a furcation unit which is compact in size (both in cross section and length) would be advantageous, as the use of fiber optic cables is increasingly common in areas of limited space. Additionally, it would desirable if the furcation unit minimized bending of the individual optical fibers, as bending may adversely affect the performance of the optical fibers.
The inventive furcation apparatus described herein provides an easily used and assembled apparatus for separating and protecting individual conductors of a multi-conductor cable such an optical fiber cable or and electrical cable with multiple conductors. The furcation apparatus does not require the use of encapsulants or specialized tools. In addition, the furcation apparatus described herein is compact in size, both in cross-section and length, thereby permitting the use of the furcation apparatus in areas of limited space.
In a preferred embodiment, the furcation apparatus includes a furcation spacer having a first end and a second end, with a plurality of passages extend through an interior of the furcation spacer from the first end to the second end. Each passage is adapted to receive an individual furcation tube of the type having reinforcing fibers. Each of the plurality of passages has a corresponding channel on an exterior surface of the furcation spacer. The channels are of a size sufficient to receive the reinforcing fibers of the furcation tubes. An index ring is positioned around the circumference of the furcation spacer and covers a portion of each of the channels in the furcation spacer. The index ring has a gap extending there through which is in parallel alignment with the channels to allow placement of the furcation tube reinforcing fibers. The index ring may then be rotated to lock the reinforcing fibers in place. The gap in the index ring may be selectively aligned with one of the plurality of channels. A clamping ring is adapted to engage with the second end of the furcation spacer, and a guard member is adapted to engage with the first end of the furcation spacer. The guard member is also configured to receive a multi-fiber optical cable of the type having reinforcing fibers. A crimping ring is provided to crimp the reinforcing fibers of the multi-fiber optical cable securely to the guard member.
The furcation apparatus is configured such that when the reinforcing fibers of the furcation tubes and the reinforcing fibers of the cable are placed under tension, the furcation spacer is placed under compressive stress. That is, the tension in the reinforcing fibers of the furcation tubes and cable is transformed into compression in the furcation spacer. Because the furcation spacer is preferably formed of a polymeric material and such materials are inherently stronger in compression than in tension, placing the furcation spacer in a state of compression reduces the likelihood that the furcation spacer may fracture in use. This greatly increases the mechanical reliability of the furcation apparatus.